1. Field of the Invention
The present invention generally involves the field of technology pertaining to the production of combustible gaseous products from the reaction of water and carbonaceous materials. More particularly, the invention relates to an improved method for the manufacture of combustible gaseous products wherein the gasification reactions are activated by means of an electric arc.
2. Description of the Prior Art
It is known to produce a combustible gas product comprised principally of hydrogen and carbon monoxide by the water gas system wherein water or steam is reacted with incandescent carbonaceous material. This is typically realized through a two-step operation wherein a bed of carbonaceous material, such as coke, is first oxidized by passing air therethrough until the material becomes incandescent and, in the second step, passing stream through the incandescent material to yield the product gases, including hydrogen and carbon monoxide according to the following chemical equation: EQU H.sub.2 O+C.fwdarw.H.sub.2 +CO
The bed of coke is cooled during the second step, and the first step of air oxidation must be repeated in order to reheat the bed.
It is also known to heat the bed of carbonaceous material electrothermally by using carbon or graphite electrodes. This is realized by placing the electrodes in contact with the material and applying a sufficient electrical potential to the electrodes, thereby causing resistive heating of the material to sufficiently elevated temperatures which result in the gasification reactions. Water required for the gasification reactions is provided in the form of injected steam or as water vapor from a reservoir disposed at the bottom of the reactor vessel. In addition to utilizing electrodes for resistive heating, it is further known to carry out the water gas reaction by utilizing an electric arc for heating the material to the required elevated temperatures.
Known methods for manufacturing combustible gases are primarily limited to very specific carbonaceous materials, such as coke or the like, and cannot be applied to the gasification of a feed source that comprises a wide variety of carbonaceous materials, particularly where the objective involves the production of a clean burning fuel gas or a clean synthesis gas for application in the chemical industry. Conventional technology has not been proven commercially successful for the efficient gasification of varied waste products, such as refuse derived fuel (RDF), and forest, industrial, or agricultural wastes. Recovery of energy from these materials is commonly accomplished by the Mass Burn process with attendant low energy recovery efficiency and residue disposal problems, or by fluidized bed combustion processes which yield a low BTU gas when operated in the gasification mode.
The technical and economic deficiencies of the prior art technology described herein for the production of combustible gases are well known. There exists a need for an energy efficient and environmentally acceptable method for the manufacture of combustible gases from a wide variety of carbonaceous materials.